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Message-Id: <1330067945-9128-6-git-send-email-santoshsy@gmail.com>
Date:	Fri, 24 Feb 2012 12:49:05 +0530
From:	Santosh Y <santoshsy@...il.com>
To:	James.Bottomley@...senpartnership.com
Cc:	linux-scsi@...r.kernel.org, linux-kernel@...r.kernel.org,
	patches@...aro.org, linux-samsung-soc@...r.kernel.org,
	arnd@...aro.org, girish.shivananjappa@...aro.org,
	saugata.das@...aro.org, vishak.g@...sung.com, venkat@...aro.org,
	k.rajesh@...sung.com, yejin.moon@...sung.com, dsaxena@...aro.org,
	ilho215.lee@...sung.com, nala.la@...sung.com,
	stephen.doel@...aro.org, sreekumar.c@...sung.com,
	Santosh Yaraganavi <santoshsy@...il.com>
Subject: [PATCH v2 5/5] Documentation: UFS Host Controller Driver

From: Santosh Yaraganavi <santoshsy@...il.com>

The document provides Universal Flash Storage(UFS) and
UFS host controller driver overview.

Signed-off-by: Santosh Yaraganavi <santoshsy@...il.com>
Reviewed-by: Vishak G <vishak.g@...sung.com>
---
 Documentation/scsi/00-INDEX |    2 +
 Documentation/scsi/ufs.txt  |   89 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 91 insertions(+), 0 deletions(-)
 create mode 100644 Documentation/scsi/ufs.txt

diff --git a/Documentation/scsi/00-INDEX b/Documentation/scsi/00-INDEX
index b48ded5..b7dd650 100644
--- a/Documentation/scsi/00-INDEX
+++ b/Documentation/scsi/00-INDEX
@@ -94,3 +94,5 @@ sym53c8xx_2.txt
 	- info on second generation driver for sym53c8xx based adapters
 tmscsim.txt
 	- info on driver for AM53c974 based adapters
+ufs.txt
+	- info on Universal Flash Storage(UFS) and UFS host controller driver.
diff --git a/Documentation/scsi/ufs.txt b/Documentation/scsi/ufs.txt
new file mode 100644
index 0000000..bd797b9
--- /dev/null
+++ b/Documentation/scsi/ufs.txt
@@ -0,0 +1,89 @@
+UFS:
+Universal Flash Storage is a storage specification for flash devices.
+It is aimed to provide a universal storage interface for both
+embedded and removable flash memory based storage in mobile
+devices such as smart phones and tablet computers. The specification
+is defined by JEDEC Solid State Technology Association. UFS is based
+on MIPI M-PHY physical layer standard. UFS uses MIPI M-PHY as the
+physical layer and MIPI Unipro as the link layer.
+
+The main goals of UFS is to provide,
+- Optimized performance:
+  For UFS version 1.0 and 1.1 the target performance is as follows,
+  Support for Gear1 is mandatory (rate A: 1248Mbps, rate B: 1457.6Mbps)
+  Support for Gear2 is optional (rate A: 2496Mbps, rate B: 2915.2Mbps)
+  Future version of the standard,
+  Gear3 (rate A: 4992Mbps, rate B: 5830.4Mbps)
+- Low power consumption
+- High random IOPs and low latency
+
+UFS Architecture Overview:
+UFS has a layered communication architecture which is based on SCSI
+SAM-5 architectural model.
+
+UFS communication architecture consists of following layers,
+
+* Application Layer: It is composed of UFS command set layer(UCS),
+  Task Manager and Device manager. The UFS interface is designed to be
+  protocol agnostic, however SCSI has been selected as a baseline
+  protocol for versions 1.0 and 1.1 of UFS protocol  layer.
+  UFS supports subset of SCSI commands defined by SPC-4 and SBC-3.
+  - UCS: It handles SCSI commands supported by UFS specification.
+  - Task manager: It handles task management functions defined by the
+    UFS which are meant for command queue control.
+  - Device manager: It handles device level operations and device
+    configuration operations. Device level operations mainly involve
+    device power management operations and commands to Interconnect
+    layers. Device level configurations involve handling of query
+    requests which are used to modify and retrieve configuration
+    information of the device.
+
+* UFS Transport Protocol(UTP) layer: UTP layer provides services for
+  the higher layers through Service Access Points. UTP defines 3
+  service access points for higher layers.
+  - UDM_SAP: Device manager service access point is exposed to device
+    manager for device level operations. These device level operations
+    are done through query requests.
+  - UTP_CMD_SAP: Command service access point is exposed to UFS command
+    set layer(UCS) to transport commands.
+  - UTP_TM_SAP: Task management service access point is exposed to task
+    manager to transport task management functions.
+  UTP transports messages through UFS protocol information unit(UPIU).
+
+* UFS Interconnect Layer(UIC): This is the lowest layer of UFS layered
+  architecture. It handles connection between UFS host and UFS device.
+  UIC consists of MIPI UniPro and MIPI M-PHY. UIC provides 2 service
+  access points to upper layer,
+  - UIC_SAP: To transport UPIU between UFS host and UFS device.
+  - UIO_SAP: To issue commands to Unipro layers.
+
+UFSHCD:
+The UFS host controller driver is based on Linux SCSI Framework.
+UFSHCD is a low level device driver which acts as an interface between
+SCSI Midlayer and PCIe based UFS host controllers.
+
+The current UFSHCD implementation supports following functionality,
+- UFS controller initialization: The initialization module brings UFS
+  host controller to active state and prepares the controller to
+  transfer commands/response between UFSHCD and UFS device.
+- UTP Transfer requests: Transfer request handling module of UFSHCD
+  receives SCSI commands from SCSI Midlayer, forms UPIUs and issues
+  the UPIUs to UFS Host controller. Also, the module decodes responses
+  received from UFS host controller in the form of UPIUs and intimates
+  the SCSI Midlayer of the status of the command.
+- UFS error handling: Error handling module handles Host controller
+  fatal errors, Device fatal errors and UIC interconnect layer related
+  errors.
+- SCSI Error handling: This is done through UFSHCD SCSI error handling
+  routines registered with SCSI Midlayer. Examples of some of the error
+  handling commands issues by SCSI Midlayer are Abort task, Lun reset
+  and host reset. UFSHCD Routines to perform these tasks are registered
+  with SCSI Midlayer through .eh_abort_handler, .eh_device_reset_handler
+  and .eh_host_reset_handler.
+
+In this version of UFSHCD Query requests and power management
+functionality are not implemented.
+
+UFS Specifications can be found at,
+UFS - http://www.jedec.org/sites/default/files/docs/JESD220.pdf
+UFSHCI - http://www.jedec.org/sites/default/files/docs/JESD223.pdf
-- 
1.7.5.4

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